Telephone-exchange system.



H. G. WEBSTER.

TELEPHONE EXGHANGB SYSTEM.

APPLICATION FILED FEB. 12, 1906.

907,659, Patented Dec. 22, 1908.

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H. G. WEBSTER. TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED FEB. 12, 1906.

907,659. Patented Dec. 22, 1908.

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UNITED STATES PATENT OFFIQEO HARRY G. WEBSTER, OF CHICAGO, ILLINOIS, ASSIGNOR 'IO MILO G. KELLOGG, OF CHICAGO, ILLINOIS.

TELEPHONE-EXCHANGE SYSTEM.

Application filed February 12, 1906.

To all whom it may concern:

Be it known that I, HARRY G. Wnissrnn, a citizen of the United States, and resident of Chicago, county of Cook, and State of Illinois, have invented new and useful Improvements in Telephone Exchange Sys tems, of which the following is a specification.

The present invention relates to telephone systems generally, and more particularly to the arrangement of circuits and apparatus by which the operator and subscriber may signal each other and by which the operator may be informed of the operative condition of a connected telephone line, and consists in a novel organization of circuits and apparatus associated with the line circuit which is utilized, together with the link-circuit and the subscribers equipment, in performing these functions.

In carrying out my invention, I arrange the cut-off and line relays so that the resistances of their windings may be utilized in the control of the supervisory signal associated with the link-circuit. This is preferably aceomplished by arranging these relays and their connections so that when the link-circuit is connected to the line by the insertion of the usual connecting plug into one of the line jacks, energizing windings of the line and cut-off relays are connected in bridge of the telephone line limbs and directly in circuit with the supervisory signal associated with the connected plug. l he closing of this circuit alone causes the display of the supervisory signal; while the usual connection of the line limbs at the substation completes a path in shunt to the line and cut-off relay windings thus connected in bridge, thereby varyin the current flow through the super visory signal sufiiciently to cause its ef'facement. In this organization, I preferably employ, for the control of the supervisory signal, a relay of the so-called double acting type, which I have disclosed in prior applications for Letters Patent. Such a relay may be varied in form, but preferably is so constructed that its contacts may be moved through a portion of their maximum range in response to a given energization, and through the remainder of the range in response to a greater energizationthe former to light a signal lamp, and the latter to extinguish it. In developing this general organization, I have devised certain novel cir- Specification of Letters Patent.

Patented Dec. 22, 1908.

Serial No. 300,702.

cuit arrangements which are not limited to the present system, but are capable of use in other relations.

The invention in its different aspects and its various subsidiary features will be more fully understood upon reference to the following detailed description, taken in connection with the accompanying drawing, and its scope will be particularly indicated in the appended claims.

In said drawing, Figure 1 is a diagram of a manually operated multiple telephone system, presenting one embodiment of my invention; and Figs. 2, 8 and 4 are diagrams of modified line circuit arrangements which may be used with the link-circuit arrangement of Fig. 1.

Referring in detail to said drawing and, for the present, to Fig. 1, A and B designate substations which are connected to the central oflice C by suitable telephone lines. The equipment at substation A, which may be of any preferred type, is here shown as embodying a call-bell 1 in series with a condenser 2, normally maintained in bridge of the telephone line limbs 34 by the engagement of the switch-hook 5 with the fixed contact 6. The transmitter 7 and the receiver 8 are connected, between the line limbs 3 and 4, in a normally open bridge which may be closed by the engagement of the switch-hook 5 with the fixed contact 9 whenever the re ceiver 8 is removed from the switch-hook 5. While the receiver remains in place, a path is provided through the call-bell 1 and condenser 2 for incoming ringing current, while its removal completes a path for battery current from a suitable central oilice source, through the transmitter and receiver. At the central office,,the telephone line limbs 3 and 4c are extended to the contacts 10 and 11 of the usual spring jacks 12 and to the terminals of a suitable source of current 13. Line limb 3 is normally connected to ground at the contacts 1% and 15 of a cut-off relay 16, but may be conductively united to the jack con tacts 11 by the movement of the contact 14 into engagement with the cut-off relay contact 17 upon the energization of said relay. The line limb 4 is connected to the live pole of the battery 13 by way of the conductors 18 and 19. The former conductor includes an energizing winding 20 of the line relay 21 and is normally united to the conductor 19 by the relay contacts 22 and 23. The conductor 19 includes an energizing Winding 24 of the line relay 21. The line signal, which is preferably an incandescent electric lamp 25, is included between the live pole of the battery 13 and ground by a normally open bridge including the conductors 26 and 27. This bridge is normally closed at the cut-ofi relay contacts 14 and 28, and is normally open at the line relay contacts 29 and 30. The energizing winding 31 of the cutoil relay 16 is permanently connected to the jack contacts 11 in an open circuit which may be closed at the line relay contacts 32 and 33 to bring'the line relay winding 20 and the cut-o6 relay winding 31 into bridge of the telephone line limbs.

The circuits and apparatus, thus far described in connection with substation A, are duplicated at substation B and are designated by similar primed characters.

At the central orlice, connection is established between the desired telephone lines by means or the link-circuit comprising the strands 34 and 35, which unite the tip contacts 36 and 37 of the answering and calling plugs 38 and 39 respectively, and the strands 40 and 41 which unite sleeve contacts 42 and 43 of said plugs. with the usual condensers 44 and 45, which permit the passage of voice currents and, by refusing the passage of battery currents, maintain the signaling apparatus at the op posite ends of the linK-circuit independent. At the answering end of the link-circuit, a double acting relay 46 is provided for the control of a supervisory signal lamp 47. The relay is provided with a winding 48, which is included between the live pole of the battery 49 and the sleeve strand 40 of the linkcircuit, and a winding 50 which is included between the grounded pole of the battery 49 and the tip strand 34 of the link-circuit. The relay contacts 51, 52 and 53 are arranged so that upon a given pull of the magnet of the relay 46, the contacts 52 and 53 will be brought into engagement to complete the circuit from the live pole of the battery, through the supervisory lamp 47, to ground and upon a further pull, will break this grounded connection by separating the contacts 51 and 52. A similar relay 46 is pro vided with windings 48 and 50, similarly connected between the battery and the sleeve and tip strands 41 and 35 of the calling plug 39, and is provided with similar contacts 51, 52 and 53 for controlling the lighting and extinguishment of the supervisory lamp 47. The strands 35 and 41 are provided with the usual listening-key levers 5455, which may be depressed to close a bridge including the operators receiver 56, a condenser 57, and the secondary winding of an induction coil 58, the operators transmitter 59 being included in a local circuit with the primary winding of the induction coil 58 and a battery 60. The strands 35 and 41 are also provided with the usual ringing key, whose levers 61 and 62 normally engage fixed contacts 63 and 64 to maintain the continuity of said strands. These levers may be depressed into engagement with the supplementary levers 65 and 66 to press the latter into engagement with the fixed contacts 67 and 68 to include ringing generator 69 in bridge of the strands 35, and 41. The engagement of the ringing key levers 61 and 62 with the supplementary levers 65 and 66 completes a second bridge including the bat tery 70 and impedances 71 and 72 located on opposite sides thereof, one pole of the battery being grounded at 73.

In the operation of the system, assuming that a party at substation A desires to converse with a party at substation B, he removes his receiver 8, thereby completing a circuit for current which 'will actuate the line relay 21 to cause the display of the line lamp 25. This circuit extends from the live pole of the battery 13, through conductor 19 including the line relay winding 24, cut-off E y contacts 23-22, conductor 18 includiiO line relay winding 20, line limbs 4 and These strands are provided 3 including the closed bridge at the substation through the receiver and transmitter, and cut-oil relay contacts 14 and 15, to ground. This will cause a flow of current through the line relay windings 20 and 24 which will act in opposition in the two windings, but, by reason of the greater number of turns on the winding 24, will sufliciently energize the relay to attract its contacts 29 and 32the former to close the local circuit of the line lamp 25, and the latter to complete the bridged connection of the winding 31 of the cut-oil relay 16. Upon observing the display of the lamp 25, the operator will insert the answering plug 38 into one of the jacks associated with the line 3 4 and thereby complete a circuit from the live pole of the battery 49, through the winding 48 of the supervisory relay 46, sleeve strand 40, plug and jack contacts 4211, energizing winding 31 of the cut-ofl relay 16, line relay contacts 3233, line relay winding 20, conductor 18, jack and plug contacts 10 and 36, strand 34 and winding 46, to the grounded side of the battery 49. This circuit will sufficiently energize the cut-ofli relay 16 to break the call lamp circuit at the contacts 1428 and to disconnect the battery 13 from the line at the contacts 22 23. will be noted that, by reason of the arrangement of the windings of the line relay and their connections, the circuit ust completed reverses the direction of current flow in the winding 20 and cuts the winding 24 out of circuit. This reversal in the winding of smaller turns produces a polarity in agreement with that previously produced by the flow of current through the winding 24 of a larger number of turns, from the battery 18. The two windings 24 and 20 are so proportioned that the energization of the winding 20 from the battery 49 will retain the line relay in its actuated position. With the line and cut-off relay contacts in this position, the switch-hook 5 at the substation A will control a path in shunt to the bridged cutoff relay winding 31 and line relay winding 20. W ith this shunt path closed, the flow of current through the windings 48 and 50 of the supervisory relay 46 will energize said relay sufficiently to separate the relay contacts 51 and 52, thus preventing the lighting of the lamp 47. If, however, the shunt path through the substation is opened, the how of current through the bridged relay windings will be sufliciently less to allow the contacts 51 and 52 to come into engagement, without allowing the contacts 52 and 53 to separate. Thus, it will be seen that the open or closed condition of the bridge at the substation will be indicated by the lighting or extinguish- 1nent of the supervisory lamp 47.

Upon establishing connection with the line 34, the operator will depress her listeningkey levers 5455 to close the bridge through her receiver 56; and after learning that the calling party desires connection with substation B, she will touch the tip contact 37 of the calling plug 39 against one of the jack contacts 11 to determine the idle or busy condition of the line 34. If this line is connected with another link-circuit, or if the subscriber at substation B has removed his receiver in the act of calling, the contact 11, touched by the tip 37, will have a potential above that of ground, due in the first instance to a flow of current from the live pole of the battery 49 associated with the linkcircuit, over its sleeve strand 40 or 41, to the connected jack contact; and in the second instance, to current from the battery 13 over conductor 19, cut offrelay contacts 23-22, line relay contacts 33 32 and cut-off relay winding 31 to the jack contact. Therefore, upon touching the tip contact 37 to the jack contact 11 of a busy line, a flow of current will result over the tip strand 35, to ground, through the supervisory relay winding 50. This will disturb the normal charge on the condenser 57 and'cause a click in the operators receiver 56. he normal charge of the condenser 57 is obtained from the battery 49 when the listening-key levers 54 and 55 are depressed.

If the operator finds that the line is idle, she will insert the calling plug 39 into the jack 12. This will at first close a circuit through the line relay 21, which will be immediately followed by the breaking of said circuit and the closing of a second circuit through the cut-off relay winding 31 and the line relay winding 20 in bridge of the line limbs 34. The first circuit will extend from the live pole of the battery 13, through the conductor 19 including the winding 24 of the line relay 21, cut-off relay contacts 2223, line relay winding 20, conductor 18, jack and plug contacts 1037, strand 7O 35, winding 50 of the supervisory relay 46,

to ground. This will energize the line relay 21 sulliciently to close its contacts 2930 and 32-33, thereby connecting the winding 31 of the cut-off relay 16, and the winding 20 of the line relay, directly in circuit with the jack contacts 101 1. As soon as this takes place, the cut-ofi relay is energized by current from the battery 49, over the sleeve strand of the link-circuit, through the 89 bridged relay windings and back over the tip strand of the link-circuit to the grounded side of the battery 49. The energization of the cut-oil relay interrupts the circuit iirst closed through both windings of the line relay, disconnects the battery 13 from the line and interrupts the circuit of the line lamp 25. With the parts in this position, the operator sends ringing current over the line limbs 34 to actuate the call-bell 1 at substation 90 B by depressing the ringing-key levers 61 and 62. At this time, in order that the line and cut-oil relays may be held in their actuated positions, the battery 70 is provided, since the depression of the ringing-key levers breaks the strands 35 and 41, thereby disconnecting the battery 49 from the line. The impedances 71 and 72 prevent the short circuiting of the generator 69. Prior to the answering of the call at substation B, and while 103 current is supplied to the line and cut-oil" relays from the battery 49, the supervisory relay 46 is sufficiently energized to complete the circuit of-the supervisory lamp 47 and thereby cause its display. As soon, how- 195 ever, as the call at substation B is answered, the shunt path through the substation is closed, and the flow of current through the windings of the supervisory relay 46 is increased sufficiently to separate the contacts 51 and 52 and thereby break the circuit of the supervisory lamp 47 to cause its extinguishrnent. With the parties thus connected, the supervisory lamps 47-47 will remain dark during conversation; but as soon 5 as either party hangs up his receiver, the associated supervisory lamp will light, and the lighting of both lamps 4747 will be an indication to the operator to disconnect.

From the previous description, it will be seen that the cut-off relay depends for its operation upon the establishment of certain conditions, these conditions being the engagement of the line relay contacts 3233 and the plug and jack contacts 42 and 11. The engagement of the former contacts is under the several control of the subscriber and operator, being operated in the former case when the subscriber removes his receiver from its hook; and in the latter case by the engagement of the plug and jack contacts 36 and 10. The other condition necessary to the operation of the cut-off relay namely, the engagement of the plug and jack contacts 42 and 11is under the sole control of the operator.

In the modified line circuit arrangement illustrated in Fig. 2, the line limbs 3 and 4 are extended, as before, to the ack contacts 10 and 11, and the substation equipment is identical. The line limb 3 is also normally connected to ground through similar contacts 14-1.5 of the cut-oil relay 16 In this case, the line relay 21 has its winding included in circuit between the line limb 4 and the live pole of the battery 13 through the cut-oil relay contacts 7475 and a resistance 7 6. The line lamp 25 is included, as before, between the live pole of the battery 13 and ground, by a normally broken bridge including the conductors 26 and 27 This bridge is normally open at the cut-off relay contacts 2930 and normally closed at the cut-off relay contacts 1428. The wind ing of the cut-off relay 16 is normally connected between the jack contact 11 and ground, by way of the cut-ofi relay contacts 7778. In the operation of this system, the closing of the bridge at the substation completes a circuit from the live pole of the battery 13 through resistance 76, cut-off relay contacts 7574, line limbs 43, cut-oil relay contacts 14 -15 to ground. The line relay is thereby energized and completes the normally broken circuit of the line lamp 25 at the contacts 29 30 causing the display of the line signal. Upon the insertion of a plug into a jack of the line, either for the purpose of answering or making a call, current will be supplied from the live pole of the battery 49, over the sleeve side of the linkcircuit, through the winding of the cut-off relay 16 cut-oil relay contacts 7778, to ground. The closing of this circuit energizes the cut-0H relay 16 suHiciently to separate its contacts 74 and 75, 77 and 78, 14 and 15 and 14 and 28 The separation of the contacts 77 and 78 is brought about by the engagement of the armature contact 74 with the movable contact 78; and as long as the relay remains energized, these contacts 74 and 78 remain in conductive engagement, thus bringing the windings of the line and cut-off relays in bridge or the telephone line limbs. The actuation of the cut-off relay similarly disconnects battery 13, interrupts the circuit of the line lamp 25 and completes the connection of the line limb 3 to the jack contact 11.

In the line circuit arrangement illustrated in Fig. 3, the line limbs are continued, as before, to the jack contacts 10 and 11, and the line limb 3 is normally connected to ground by the contacts 14 and 15 of the cut-off relay 16 The line relay 21 has its winding connected in circuit between the line limb 4 and the live pole of the battery 13 by way of the cut-off relay contacts 7 9-80. This path also includes the line signal lamp 253". The circuit of the line signal lamp 25 is continued from the live pole of the battery 13* to ground by way of the normally closed cut-oil relay contacts 7 98081 and the normally open line relay contacts 29 -30 A resistance 82 is included between the line relay contact 30 and ground. When the cutofl' relay 16 is energized, the contact 14 engages the contact 17 to short circuit the lower half 83 of the winding of the cut-ofi relay, and the contact 79 engages the fixed contact 84 to include the upper half 85 of the cut-oil relay winding and the winding of the line relay 21 in bridge of the telephone line limbs. In this system, upon closing the bridge at the substation between the line limbs 3 and 4, current is supplied from the battery 13 through the lamp 25 cut-off relay contacts 80-79, line relay winding, line limbs 4 and 3, cut-oil relay contacts 14 and 15 to ground. The closing of this circuit energizes the line relay 21 sufficiently to complete the circuit of the line lamp 25 through the line relay contacts 29 *30 and resistance 82 to cause said lamp to light, as a signal to the operator that connection is desired. Upon the operator inserting a plug into a jack, either in answering or making a call, current will be supplied from the battery 49, over the sleeve side of the linkcircuit, through the lower half 83 of the cutoii relay winding, to ground by way of the cut-o1T relay contacts 14 15 thus energizing the cut-0H relay to attract its movable contacts 14 and 79. As indicated diagrammatically by the spring on the contact 14 this contact is arranged to leave the contact 15 only after the contact 79 has engaged the contact 84. The engagement of the contacts 7 9 and 84 completes a bridge between the telephone line limbs, through the upper half 85 of the winding of the cut-off relay and the winding of the line relay. The completion of this second circuit, prior to the short circuiting of the lower half 83 of the winding of the cut-off relay, retains the contacts 14 and 79 in their attracted positions. The attraction of the contact 79 breaks the circuit of the lamp 25 and, by short circuiting the lower half 83 of the winding of the cut-off relay, removes its impedance from the line limb 3 and thereby from the talking circuit.

In the line circuit arrangement illustrated in Fig. 4, the line limbs 3 and 4 are continued, as before, to the ack contacts 10 and 11, but the line limb 3 is notnormally connected directly to ground as in the previous cases, but is connected by way of the cut-off relay contacts 1415 and conductor 86, including a winding 87 of the line relay, to the live pole cuit.

of the battery 13. The call signal lamp 25 is included in circuit between the live pole of contact of the jack is raised above its normal ground potential only after the connecting the battery 13 and ground, by way of the l plug of a line circuit has been inserted, and

line relay contacts 29 and 30in this case, a single break only being provided in its cir- In this instance, the cut-cit relay 16 has its winding included in circuit between the jack contacts 11 and one strand of a twin winding 88 on the core of the line relay 21". ihe center of the twin winding is connected to ground by way of the cut-off relay contacts 89 and 90, and the other strand is connected to the line limb 4. Elle cutot": relay contact 14, when in its alternate position, engages the fixed contact 17 to connect the line limb 3 directly to the contacts 11 of associated jacks. In the operation of this system, the closing of the bridge at the substation completes a circuit from the live pole of the battery 13, through the conductor 86 including the winding 87 of the line relay, cut-oti relay contacts 1514, line limbs 3-4, one strand of the twin winding 88 and cut-ofi relay contacts 899O to ground. T he completion of this circuit energizes the line relay sutiiciently to close the circuit ofthe line lamp 25 at the contacts 29 -302 thus causing the display of the line signal. Upon the insertion of the plug, either in answering or making a call, current is supplied from the battery 49, over the sleeve side of the link-circuit, through the winding of the cut-off relay 16, the connect ed strand of the twin winding 88 and the cut-oii relay contacts 89-9G to ground. The closing of this circuit actuates the cutoff relay 16 thereby breaking the grounded connection to the center of the twin winding, disconnecting the battery 13 from the line, and depr'ving the line relay winding 87 of current. 'lhe removal of the ground connection to the twin winding permits the current to flow through both conductors of said winding and back over the tip strand of the link-circuit to the grounded side of the battery 49. Thus, it will be seen that the twin winding 88 of the line relay 21, and the winding of the cut-off relay 16, are included in bridge of the telephone line limbs and the resulting magnetic eil'ect of one conductor of the twin winding neutralizes that of the other so that the relay contacts 29 and 30 are free to separate and break the circuit of the line lamp 25.

In each of the forms illustrated in Figs. 2, 3 and 4, as well as in that illustrated in Fig. 1, the connection of the link-circuit to the line immediately operates to connect the relay windings in bridge of the telephone line; and as soon as they are so connected, the associated supervisory signal will be displayed or efiaced, according to whether the bridge at the substation is open or closed. In each of the line circuit arrangements illustrated in Figs. 2, 3 and 4, the potential of the testing not also in response to the removal of the receiver from its switch-hook at the substation, as is the case in the arrangement illustrated in Fig. 1. 'lhe testing operation on the part of the operator, however, is the same.

In the diagrams, the various ground connections should be understood as represent ing connections to ground or the usual common return of a central oifice; and in each instance, the various batteries, instead of beingseparate and distinct as shown, may be one and the same. it is also obvious that other alterations and modifications may be made in the matter disclosed without departing from the spirit and scope of my invention. I, therefore, do not wish to be limited to the specific matter illustrated, but aim to cover, by the terms of the appended claims, all such alterations and modifications.

In the accompanying claims I have used the term cut-on in a broad sense to define that relay which, when operated, removes the control of the line signal from the subscriber.

"W hat I claim as new and desire to secure by Letters Patent of the United States is 2- 1. A telephone system comprising a telephone line extending from a substation to a central otlice, a line signal associated therewith, electromagnetically actuated means for normally controlling the display of said signal, electromagnetically actuated means for destroying said control, one of said means having its' energizing winding normally disconnected irom said line, a link-circuit for making connection to said line, means for holding conversation over said line and linkcircuit, a source of current, and means operative upon the connection of said link-circuit to said line to connect energizing windings of both of said electromagnetically actuated means in series bridge of said telephone line and in series with said source of current.

2. A telephone system comprising a telephone line extending from a substation to a central otfice, a line signal associated therewith, electromagnetically actuated means for normally controlling the display of said signal, electromagnetically actuated means for destroying said control, a link-circuit for making connection to said line, means for holding conversation over said line and linkcircuit, a supervisory signal associated with said link-circuit, and means operative upon the connection of said link-circuit to said line to complete a control circuit for said supervisory signal through energizing windings of both of said electromagnetically actuated means in series bridge of said telephone line.

3. A telephone system comprising a telephone line extending from a substation to a central oflice, a line signal associated therewith, a line relay for normally controlling the display of said signal, a cutofi' relay having its energizing Winding normally disconnected from said line and operative to destroy said control, a link-circuit for making connection to said line, means for holding conversation over said line and link-circuit, a source of current, and means operative upon the connection of said link-circuit to said line to connect energizing windings of said cut-oil and line relays in series bridge of said telephone line and in series with said source of current.

4. A telephone system comprising a telephone line extending from a substation to a central oliioe, a line signal associated there with, a line relay for normally controlling the display of said signal, a cutoff relay for destroying said control, a link-circuit for making connection to said line, means for holding conversation over said line and link-circuit, a supervisory signal associated with said linkcircuit, and means operative upon-the con nection of said link-circuit to said line to complete a control circuit for said supervisory signal through energizing windings of said cut-oil. and line relays in series bridge of said telephone line.

5. A telephone system comprising a telephone line extending from a substation to a central oilice, a line signal associated therewith, a line relay for normally controlling the display of said signal, a cut-off relay having its energizing winding normally disconnected from said line and operative to destroy said control, a link-circuit for making connection to said line, means for holding conversation over said line and link-circuit, means operative upon the connection of said link-circuit to said line to complete a circuit over portions of the connected line limbs and through energizing windings of said cut-0H and line relays, means under the control of the subscriber for closing a path in shunt to said energizing windings, and means associated with said link-circuit for displaying a signal in response to the closing of said first-mentioned circuit and eflacing said signal in response to the additional closing of said shunt path.

6. A telephone system comprising a telephone line extending from a substation to a central oliice, a line signal associated therewith, a line relay for normally controlling the display of said signal, a cut-oii relay for destroying said control, a link-circuit for making connection to said line, means for holding conversation over said line and link-circuit, electrically actuated signal mechanism associated with said link-circuit and responsive to a given current flow through its winding to display its signal and to a different current flow to eilace said signal, means operative upon the connection of said link-circuit to said line to cause the display of said signal by completing a circuit over portions of the connected line limbs and through energizing I windings of said cut-oii and line relays in l series, and means under the control of the subscriber for efiacing said signal by varying the current through the winding of its mechamsm.

phone line extending from a substation to a central ollice, a line signal associated therewith, a line relay for normally controlling the display of said signal, a cut-off relay for destroying said control, a link-circuit for making connection to said line, means for holding conversation over said line and link-curcuit, electrically actuated signal mechanism associated with said link-circuit and responsive to a given current flow through its winding to display its signal and to a greater current flow to eflace said signal, means operative upon the connection of said link-circuit to said line to cause the display of said signal by completing a circuit over portions of the connected line limbs and through energizing windings of said cut-oil and line relays, and means under the control of the subscriber for efi'acing said signal by increasing the current in the winding of its mechanism.

8. A telephone system comprising a telephone line extending from a substation to a central oliice, a line signal associated therewith, a line relay for normally controlling the display of said signal having two energizing windings, a cut-01f relay for destroying said control, means under the control of the subscriber for normally closing a circuit through both windings or said line relay to actuate it to cause the display of said signal, and means under the control of the operator forinterrupting said subscribers circuit and connect- 1 ing one winding of said line relay and an energizing winding of said cut-off relay in bridge of said telephone line.

9. A telephone system comprising a telephone line extending from a substation to a central office, a line signal associated therewith, a line relay for normally controlling the display of said signal having two energizing windings, a cut-oil relay for destroying said control, means normally under the control of the operator for closing a circuit at first through both windings or said line relay, and electromagnetically actuated means for subsequently connecting one winding of said relay and an energizing winding of said cut-oli relay in bridge of said telephone line.

10. A telephone system comprising a telephone line extending from a substation to a central ollice, a line signal associated therewith, a line relay for normally controlling the display of said signal, a cutofi relay for destroying said control, a link-circuit for making connection to said line, means for holding conversation over said line and link-circuit, means operated upon the connection of said l link-circuit to said line both to complete an 7. A telephone system comprising a teleenergizing circuit for said line relay and to close a portion of an energizing circuit for said cut-off relay, and means actuated by said line relay to complete the said cut-oil relay circuit.

11. A telephone system comprising a telephone line extending from a substation to a central ofiice, a line signal associated there with, a line relay for normally controlling the display of said signal, a cut-off relay for destroying said control, -a link-circuit for mak ing connection to said line, means for holding conversation over said line and link-circuit, means operated upon the connection of said link-circuit to said line both to complete an energizing circuit for said line relay and to close a portion of an energizing circuit for said cut-oil relay, means actuated by said line relay for completing said cut-oil relay circuit, and means normally under the control of the subscriber for actuating said line relay.

12. A telephone system comprising a telephone line extending from a substation to a central eflice, a line signal associated there with, a line relay for normally controlling the display of said signal, a cut-oft relay for destroying said control, a link-circuit for making connection to said line, means for holding conversation over said line and link-circuit, means operated upon the connection of said linl -circuit to said line both to complete an energizing circuit for the line relay including a portion of one connected line limb and to close a portion of an energizing circuit for said cut-off relay including a portion of the other connected line limb, and means actuated by said line relay for completing said cut-ofi' relay circuit.

13. A telephone system comprising a telephone line extending from a substation to a central ofiice, a line signal associated therewith, a line relay for normally controlling the display of said signal, a cut-off relay for destroying said control, a link-circuit for making connection to said line, means for holding conversation over said line and link-circuit, means operated upon the connection of said link-circuit to said line both to complete an energizing circuit for the line relay including a portion of one connected line limb and to close a portion of an energizing circuit for said cut-oil relay including a portion of the ther connected line limb, means actuated by said line relay for completing said cut-oil relay circuit, and means normally under the control of the subscriber for actuating said line relay.

14. A telephone system comprising a telephone line extending from a substation to a central office, a line signal associated therewith, a line relay for normally controlling the display of said signal, a cut-oil relay for destroying said control, a link-circuit for making connection to said line, means for holding conversation over said line and linkcircuit, means operative upon the connection of said link-circuit to said line both to complete an energizing circuit for the line relay including a portion of one connected line limb and to close a portion of a energizing circuit for said cut-oil relay including a portion of the other connected line limb, means actuated by said line relay to complete said cut-off relay circuit, means under the control of the subscriber for completing a path in shunt to a portion of said completed cutofl relay circuit, and means associated with said link-circuit for displaying a signal in resn'onse to the completion of said cut-oil relay circuit and for e'rl'acing said signal in response to the additional closing of said shunt path.

15. A telephone system comprising a telephone line extending from a substation to a central oiiice, a line signal associated therewith, a line relay for normally controlling the display of said signal, a cut-oil relay for destroying said control, a link-circuit for making connection to said line, means for holding conversation over said line and link-circuit, means operative upon the connection of said link-circuit to said line both to complete an energizing circuit for the line relay including a portion of one connected line limb and to close a portion of an energizing circuit for said cut-oii relay including a portion of the other connected line limb, means actuated by said line relay to complete said cutofl relay circuit, means under the control of the subscriber operative normally to close an energizing circuit for said line relay and operative, when connection is established between said link-circuit and line, to close a path in shunt to a portion of the completed cut-off relay circuit, and means associated. with said link-circuit for displaying a signal in response to the completion of said cut-oil relay circuit and for eilacing said signal in response to the additional closing of said shunt path.

16. A telephone system comprising a telephone line extending from a substation to a central office, a line signal associated therewith, a line relay for normally controlling the display of said signal, a cut-oil relay for destroying said control, a link-circuit for making connection to said line, means for holding conversation over said line and link-circuit, electrically actuated signal mechanism associated with said linkcircuit and responsive to a given current flow through its winding to display its signal and to a diilierent current flow to e'll'ace said signal, means operative upon the connection of said link-circuit to said line both to complete an energizing circuit for the line relay including a portion of one connected line limb and to close a portion of an energizing circuit for said cut-off relay and for said electrically actuated signal mechanism including a portion of the other connected line limb, means actuated by said line relay to complete said cut-oil relay circuit to actuate said cut-oii relay and to display said link-circuit signal, and means under the control of the subscriber for eii'acing said linkcircuit signal by varying the current through the winding of its mechanism.

17. A telephone system comprising a telephone line'extending from a substation to a central Office, a line signal associated therewith, a line relay for normally controlling the display of said signal, a cut-oil relay for destroying said control, a link-circuit for making connection to said line, means for holding conversation over said line and link-circuit, electrically actuated signal mechanism associated with said linkcircuit and responsive to a given current flow through its winding to display its signal and to a greater current flow to eflace said signal, means operative upon the connection of said link-circuit to said line both to complete an energizing circuit for the line relay including a portion of one connected line limb and to close a portion of an energizing circuit for said cut-oil relay and for said electrically actuated signal mechanism including a portion of the other connected line limb, means actuated by said line relay to complete said cut-oil relay circuit to actuate said cut-ofi relay and to display said linkcircuit signal, and means under the control of the subscriber for eflacing said link-circuit signal by increasing the current through the Winding of its mechanism.

18. A telephone system comprising a telephone line extending from a substation to a central office, a line signal associated therewith, a line relay for normally controlling the display of said signal, a cut-off relay for destroying said control, a link-circuit for making connection to said line, means for holding conversation over said line and link-circuit, electrically actuated signal mechanism associated with said linkcircuit and responsive to a given current flow through its winding to display its signal and to a different current flow to efl'ace said signal, means operative upon the connection of said link-circuit to said line both to complete an energizing circuit for the line relay including a portion of one connected line limb and to close a portion of an energizing circuit for said cut-off relay and for said electrically actuated signal mechanism including a portion of the other connected line limb, means actuated by said line relay to complete said circuit to actuate said cut-ofi relay and to display said link-circuit signal, and means under the control of the subscriber operative normally to close an energizing circuit for said line relay and operative, when connection is established between said link-circuit and line, to eflace said linkcircuit signal by varying the current through the winding of its mechanism.

19. A telephone system comprising a telephone line extending from a substation to a central ofiice, a line signal associated therewith, a line relay for normally controlling the display of said signal, a cut-off relay for destroying said control, a linkcircuit for making connection to said line, means for holding conversation over said line and link-circuit, electrically actuated signal mechanism associated with said linkcircuit and responsive to a given current flow through its winding to display its signal and to a greater current flow to e'liace said signal, means operative upon the connection of said link-circuit to said line both to complete an energizing circuit for the line relay including a portion of one connected line limb and to close a portion of an energizing circuit for said cut-ofl relay and for said electrically actuated signal mechanism including a portion of the other connected line limbs, means actuated by said line relay to complete said cut-oil relay circuit to actuate said cut-oii relay and to display said linkcircuit signal, and means under the control of the subscriber operative normally to close an energizing circuit for said line relay and operative, when connection is established between said link-circuit and line, to efiace said link-circuit signal by increasing the current through the winding of its mechanism.

20. A telephone system comprising a telephone line extending from a substation to a central oflice, a line signal associated therewith, a line relay for normally controlling the display of said signal having two energizing windings, a cut-ofl relay for destroying said control, means under the control of the subscriber for normally closing a circuit through both windings of said line relay to actuate it to cause the display of said signal, means under the control of the operator for closing a circuit through both windings of said line relay and electromagnetically actuated means for subsequently closing a circuit through an energizing winding of said cut-oli relay.

21. A telephone system comprising a telephone line extending from a substation to a central office, a line signal associated therewith, a line relay for normally controlling the display of said signal having two energizing windings, a cut-oil? relay for destroying said control, means under the control of the subscriber for normally closing a circuit through both windings of said line relay to actuate it to cause the display of said signal, means under the control of the operator for closing a circuit through both windings of said line relay, and electromagnetically actuated means for subsequently closing a circuit through 1 under the control of the operator for normally one of said windings only and an energizing winding of said cut-oil relay.

22. A telephone system comprising a telephone line extending from a substation to a central ofiice, a line signal associated therewith, a line relay for normally controlling the display of said signal having two energizing windings of different numbers of turns, a cutofi relay for destroying the normal line relay l control of said signal, means under the control of the subscriber for normally closing a circuit through both windings of said line relay to actuate it to cause the display of said signal, and means under the control of the operator for closing a circuit at first through both windings of said line relay, and subsequently through the winding of a lesser number of turns of said line relay and an energizing winding of said cut-off relay.

23. A telephone system comprising a telephone line extending from a substation to a central oflice, a line signal associated therewith, a line relay for normally controlling the display of said signal having two energizing windings, a cut-oii relay for destroying said control operative only when said line relay is in its actuated position, means under the control of the subscriber for normally closing a circuit through both windings of said line relay to actuate it to cause the display of said signal, and means under the control of the operator for interrupting the subscribers circuit through both windings of said line relay and closing a circuit through one of said windings to maintain said line relay in its actuated position.

24. A telephone system comprising a telephone line extending from a substation to a central oflice, a line signal associated therewith, a line relay for normally controlling the display of said signal having two energizing windings, a cut-ofi relay for destroying said control operative only when said line relay is in its actuated position, means under the control of the subscriber for normally closing a circuit through both windings of said line relay' to actuate it to cause the display of said signal, and means under the control of the operator for interrupting the subscriber s circuit through both windings of said line relay and closing a circuit through one of said windings and through an energizing winding of said cut-oii relay to maintain the line relay in its actuated position and to actuate said cut-off relay.

25. A telephone system comprising a telephone line extending from a substation to a central ofiice, a line signal associated therewith, a line relay for normally controlling the display of said signal having two energizing windings, a cut-ofi reay for destroying said control operative only when said line closing a circuit through both windings of said line relay to actuate it and subsequently closing a circuit through one only of said windings to maintain said line relay in its actuated position.

26. A telephone system comprising a telephone line extending from a substation to a central office, a line signal associated therewith, a line relay for normally controlling the display of said signal having two energizing windings, a cut-oil relay for destroying said control operative only when said line relay is in its actuated position, means under the control of the operator for normally closing a circuit through both windings of said line relay to actuate it, and electromagnetically actuated means for subsequently closing a circuit through one of said windings and through an energizing winding of said cutofi relay to maintain said line relay in its actuated position and to actuate said cut-off relay.

27 A telephone system comprising a telephone line extending from a substation to a central office, a line signal associated therewith, a line relay for normally controlling the display of said signal having two energizing windings of different numbers of turns, means under the control of the subscriber for closing a circuit through said windings in opposition to actuate said relay to cause the display of said signal, and means under the control of the operator for cutting said line relay winding of a greater number of turns out of circuit and reversing the direction of current flow in said winding of a lesser number of turns, thereby to maintain said relay in its actuated position. 7

28. A telephone system comprising a telephone line extending from a substation to a central ofiice, a line signal associated therewith, a line relay for normally controlling the display of said signal having two energizing windings of difl'erent numbers of turns, a cutoff relay for destroying said control operative only when said line relay is in its actuated position, means under the control of the sub scriber for closing a circuit through the windings of said line relay in opposition to actuate said relay to cause the display of said signal, and means under the control of the operator for cutting said line relay winding of a greater number of turns out of circuit and reversing the direction of current flow in said winding of a lesser number of turns, thereby to maintain said relay in its actuated position.

29. A telephone system comprising a telephone line extending from a substation to a central office, a line signal associated therewith, a line relay for normally controlling the display of said signal having two energizing windings of diflerent numbers of turns, a cut relay is in its actuated position, and means i ofi relay for destroying said control operative only when said line relay is in its actuated position, means under the control of the subscriber for closing a circuit through the windings of said line relay in opposition to actuate said relay to cause the display of said signal, and means under the control of the operator for cutting said line relay winding of a greater number of turns out of circuit and reversing the direction of current how in said winding of a lesser number of turns by including it in circuit with an energizing winding of said cut-off relay, thereby to maintain said line relay in its actuated position and to actuate said cut-off relay.

30. A telephone system com rising a telephone line extending in two lim s from a substation to a central oifice, a connection ter minal for said line having a testing contact, a battery, means under the control of the subscriber for establishing a definite busy con-. nection between said testing contact and onepole. of said battery, means for enabling the. operator to determine the idle or busy condition of the line by touching the tip of the connecting plug to said testing contact, and means responsive to the connection of said line and link-circuit to interrupt said definite busy connection between said testing contact and battery.

31. A telephone system comprising a telephone line extending in two limbs from a substation to a central office, a connection terminal for said line having a testing contact, a battery, a two-strand link-circuit and connecting plug for establishing connection with saidline, a relay operative, when energized, to establish a definite busy connection between said testing contact and one ole of said battery, means under the contro of the subscriber for energizing said relay, means for enabling the operator to determine the idle or busy condition of the line by touching the tip. of the connecting plug to said testing contact, and means res onsive to the connection of said line and ink-circuit to interrupt said definite busy connection between said testing contact and battery.

32. A telephone system comprising a telephone line extending in two limbs from a substation'to a central ofiice, a connection terminal therefor, having a testing contact, a battery, a two-strand link-circuit and two.- contact connecting lug for establishing cons nection with said ine, a signal associated with said line, a line relay for normally controlling the display of said signal, a cut-oil relay for destroying said control, means actuated by the energization of said line relay to establish a definite busy connection between said testing contact and one pole of said battery, means under the control of the subscriber for energizing said line relay, I means. for enabling the operator to deterl mine the idle or busy condition of the line by touching the tip of the connecting plug to said testing contact, and means responsive to the connection of said line and link-circuit to interrupt said definite busy connection between said testing contact and battery.

33. A telephone system comprising a telephone line extending from a substation to a central oihce, connection terminals therefor, a link-circuit and connecting plug for establishing connection with said line, a signal associated with said line, a line relay for normally controlling the display of said signal, a cut-oil relay for destroying said control, means actuated by the energization of said line relay to modify the connections of the. testing contacts of said terminals to vary their potential and to connect the energizingwindings of said line and cut-off relays in bridge of said connection terminals, means under the control of the subscriber for energizing said line relay, and means for enabling the operator to determine the idle or busy condition of the line by touching the tip of the connecting plug to one of said contacts.

34. A telephone system comprising a telephone line extending from a substation to a central O'H'lCG, a line signal associated therewith, a line relay for normally controlling the display 01 said signal having two energizing windings, a cut-0d relay for destroying said control, means normally under the control of the operator for closing a circuit through both windings of said line relay and electro-. magnetically actuated means for subsequently connecting one Winding of said line relay and an energizing winding of said cutof relay in series bridge of said telephone line.

35. A telephone system comprising a telephone line extending from a substation to a central oflice, a line signal associated therewith, a line relay for normally controlling the display of said signal having two energizing windings, a cut-off relay for destroying said control, means under the control of the subscriber for normally closing a circuit through both windings of said line relay to actuate it. tocause the display of said signal, and means under the control of the operator for closing a circuit at first through both windings of said line relay and subsequently through one of said windings only and an energizing winding of said cut-ofl relay.

36. A telephone system comprising a telephone line extending from a substation to a central ofiice, a line signal associated there with, a line relay for normally controlling the display of said signal having two energizing windings, a cut-off relay for destroying said control operative only when said line relay is in its actuated position, means under the control of the operator for normally closing a circuit at first through both In Witness whereof, I hereunto subscribe windings of said line relay to actuate it and my name this 8th day of February, A. D.,

subsequently through one of said windings 1906. only and an energizing Winding of said cut- HARRY G. WEBSTER. off relay to maintain said line relay in its ac- Witnesses:

tuated. position and to actuate said cut-05 A. H. DYsoN, relay.

CAROLYN WEBER. 

